DEA-C01 Cross-region read replica Practice Question
A data engineering team is responsible for an Amazon RDS for PostgreSQL instance that stores financial data. The database is 500 GB in size. The team needs to create a read replica in a different AWS Region for disaster recovery. The source database has automated backups enabled with a retention period of 7 days. The team initiates the cross-region read replica creation. After several hours, the replica status shows 'Replication Lag' of 30 minutes and is increasing. What should the team do to reduce the replication lag?
⚠ Common exam trap
Candidates might think enabling Multi-AZ on the source database could reduce cross-region replication lag because it introduces a standby that might appear to offload work. In reality, Multi-AZ replicates synchronously to the standby for high availability, but cross-region read replicas replicate asynchronously directly from the primary. Multi-AZ can actually increase I/O load on the primary, potentially worsening replication lag. A larger source instance can help if the primary is under-provisioned.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the source DB instance to use a larger instance class.
Modifying the source DB instance to a larger instance class provides more compute and memory resources. If the source instance is resource-constrained, this can reduce I/O contention and allow it to generate and ship write-ahead logs (WAL) more efficiently, potentially decreasing the replication lag to the cross-region read replica. Enabling Multi-AZ on the source database adds a synchronous standby in a different Availability Zone, which does not offload cross-region replication tasks and can increase write latency and resource overhead on the primary, possibly exacerbating replication lag. Deleting and recreating the replica from a snapshot or increasing backup retention does not address ongoing replication performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the source DB instance to use a larger instance class.
Why this is correct
A larger instance class can increase source performance, allowing faster WAL generation and shipping, which may reduce replication lag if the source is bottlenecked.
- ✗
Delete the replica and create a new one from a snapshot.
Why it's wrong here
Deleting and recreating the replica from a snapshot does not affect the ongoing replication lag; it starts a new replica with eventual catch-up.
- ✗
Increase the backup retention period to 35 days.
Why it's wrong here
Increasing backup retention period has no impact on replication lag, as backups are taken from the database via snapshot mechanisms unrelated to replication.
- ✗
Enable Multi-AZ on the source database instance.
Why it's wrong here
Enabling Multi-AZ adds a synchronous standby but does not reduce cross-region replication lag; it may increase resource overhead on the primary, potentially worsening lag.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.